At the beginning on November, Bertha the tunnel boring machine hit the mile-mark in her 9,270-foot-long trip across Downtown Seattle. Now comes word that as of Monday she has mined 5,774 feet and installed 880 of the 1,426 concrete tunnel rings needed to complete the journey.
Now, Bertha is going to hit a new low. We mean that literally.
With the top of the cutterhead now approximately 210 feet below the surface, crews are nearing the deepest point of the tunnel drive.
WSDOT notes that the deepest point overall will be 265 feet down.
The machine is now in what WSDOT calls Zone 7 (out of 10). She’s begun veering east from First Avenue towards Second Avenue at Lenora Street. At the 6,095-foot mark she will have completed this zone and moved into the next one, in which she’ll begin her ascent back towards the surface.
Work halts now for Thanksgiving but will resume next Monday.